Exclusive production of $\rho$ meson in gamma-proton collisions: $d \sigma/dt$ and the role of helicity flip processes

TL;DR

This paper models the differential cross section for rho meson production in gamma-proton collisions, emphasizing the significance of helicity flip processes and their dependence on nonperturbative gluon distributions, aligning with recent CMS data.

Contribution

It introduces a model incorporating helicity flip amplitudes in rho meson production, highlighting their impact on the differential cross section at finite momentum transfer.

Findings

Helicity flip processes significantly influence the shape of the differential cross section.

The unintegrated gluon distribution's transverse momentum dependence is crucial.

Model aligns well with recent CMS experimental data.

Abstract

We calculate the differential cross section $d\sigma/dt$ for the diffractive photoproduction process $\gamma p \to \rho p$ and compare to recent data extracted by the CMS collaboration from ultraperipheral proton-lead collisions. Our model is based on two-gluon exchange in the nonperturbative domain. We take into account both helicity conserving and often neglected helicity-flip amplitudes in the $\gamma \to V$ transition. The letter can contribute at finite $t$. The shape of the differential cross section as well as the role of helicity flip processes is strongly related to the dependence of the unintegrated gluon distribution on transverse momenta in the nonperturbative region.